86 Theories and techniques of oral implantology

plant. This was his twentieth insertion of such an implant. Then he gave 600,000 units of penicillin. On April 3, not having seen any postoperative disorder, he set a resin crown with supporting rests on the neighboring canine and second premolar to limit irnplant mobility. He again injected 600,000 units of penicillin. On April 4 chewing was almost normal, with a slight sensation of quaintness, or newness, but without any spontaneous or pressure pain. Then he took the radiograph shown in Fig. 4-7.

As can be seen on the radiograph, Perron-Andres implanted a short spiral. The first spiral is flush with the alveolar ridge, though from the apex to the maxillary sinus floor there are at least 6 mm. that could have been utilized for inserting a long implant deeper.

The patient, a personal friend of Perron-Andres, was asked if she would be willing, at a later date, to experimentally exchange her implant for a longer one, even if the first one was functioning well. She was very cooperative and agreed to do so.

At the beginning of May, Perron-Andres started the patient on twenty calcium cartridges intramuscularly, one each day. The implant stayed immobile and did not show, more than a month and a half after its setting, the characteristic mobility that usually starts between the tenth and the twenty-fifth days with a failing implant. At the end of June, the patient reported that during a period of intense study and strong nervous tension, she had become conscious of her implant without its being painful or preventing chewing.

In August, the implant showed the "stable mobility" normally seen in most cases of an isolated tooth, and on October 5, a radiograph of the implant showed considerable osseous rarefaction involving almost half of the spiral portion. The third spiral was surrounded, on its mesial surface, by a radiotransparent zone about 1 mm. wide. Only the last spiral was enclosed in healthy bone. The next day, 6 months after its insertion, Perron-Andres re-moved the implant, using infiltration anesthesia.

At the beginning of the removal procedures, the implant presented noticeable elastic resistance to the traction exerted. The resistance was such that, after a 90-degree turn, when the vestibular face was in a mesial position, the implant twisted away from the pliers and rotated back into its original position between the neighboring teeth. For a moment, Perron-Andres feared that he would shatter the resin crown. However, pulling with sufficient force, he mobilized the implant again and unscrewed it without stop-

ping. With each turn he felt considerable resistance along the axis as well as in the direction in which the implant was being unscrewed. The resistance continued until the implant was completely liberated. Such strong resistance in a failing Formiggini implant is a result of a peculiarity of its structure. An "ear" is formed by the way the axial wire joins the peripheral one. When fibrous tissue forms around the ear, as well as between the spirals and around the axis, it is almost impossible to remove the implant without tearing the tissue.

When he had removed the implant, Perron-Andres immediately proceeded to obtain a biopsy sample from the site. Using a cataract bistoury, he cut circularly and as closely as possible to the osseous walls. He gradually dug toward the apex, which he cut with a curved bistoury. The resulting extracted section was a conical piece slightly longer than the spiral and with a diameter smaller toward the apex. The lack of definition of the implant site in the prepared sections can be explained by the tearing of tissue caused by the apical ear. However, the basic histologic picture was unaffected by the tearing, and Perron-Andres was thus able to draw conclusions about the role of the membrane in offering resistance to extraction, an important consideration from a clinical point of view.

The histologic studies were done for Dr. Perron-Andres by the Spanish pathologist, Dr. Alcober Coloma, who summarized his results as follows*:

Filling tissues are connective, generally rather fibrillar, and poorly cellular. There is not particular organization in the sheaths of neoformed fibers. In some isolated places, the connective tissue is younger and more filled with cells. Also, in different places, there are small infiltrations which have a lymphocytic aspect and which some-times follow areas of the fibrous tissue that is undergoing hyalinization.

In marginal regions are found some osseous trabeculae, calcified and unaltered. Around them no phenomenon of great osteoblastic activity is seen; secondarily some osteoformation organization appears. At the end of the fragment are found particles of pavimentous lining without important alteration, hut covering points where lymphocytic infiltration reaction is very small.

To recapitulate, the filling tissues are principally made of dense fibrous connective tissue sheaths without special organization. The presence of osseous trabeculae enclosed in connective tissues

*Chercheve, R.: Les implants endo-osseoux, Paris, 1962, Librairie Maloine.